The present invention generally relates to an exhaust gas purifying apparatus for an automobile internal combustion engine and, more particularly, to a catalytic converter utilizing at least two, in-line monolithic catalyst carriers.
In order to improve the handling capacity of the catalytic converter with respect to a relatively large amount of exhaust gases emitted from an automobile internal combustion engine, the employment of two or more catalyst carriers in one catalytic converter has recently been practiced. The principle lies in that, if the exhaust gases are allowed to pass through as many catalyst carriers containing identical or different catalysts as possible, the exhaust gases can be highly purified.
Where a plurality of catalyst carriers, for example, two catalyst carriers, are employed in one converter housing, it is a conventional practice to use a spacer for holding the catalyst carriers in spaced relation to each other within the housing. In addition, in certain types of conventional catalytic converters, the supply of fresh air, i.e., secondary air, into the space between the catalyst carriers is required to increase the handling capacity of the catalytic converter. This is particularly true where the catalyst carriers positioned on upstream and downstream sides with respect to the direction of flow of the exhaust gases contain reducing and oxidizing catalysts, respectively.
Examples of the prior art catalytic converters utilizing the at least two catalyst carriers with the spacer positioned therebetween, which appear to be pertinent to the present invention, are disclosed in, for example, the U.S. Pat. No. 4,049,388, patented Sept. 20, 1977, and U.S. Pat. No. 4,238,456 patented Dec. 9, 1980.
According to the first mentioned U.S. patent, the supply of secondary air into the space between the reducing and oxidizing catalyst carriers within the housing is effected by means of a piping protruding outwardly from a portion of the housing in a direction opposite to and in alignment with the space between the catalyst carriers. The spacer used therein comprises a pair of mating manifold stampings each having a generally cylindrical connection flange and an outwardly flared wall, the cylindrical connection flange of one manifold stamping being inserted into the cylindrical connection flange of the other manifold stamping with the respective outwardly flared walls extending in opposite directions so as to diverge from the associated connection flanges. In order for the supplied secondary air to enter from the exterior of the spacer into the interior of the spacer, the connection flange of one manifold stamping has a plurality of apertures defined therein whereas the connection flange of the other manifold stamping has a corresponding number of slots defined therein. In an assembled condition of the spacer, the slots and the apertures are exactly aligned with each other.
The catalytic converter according to the first mentioned U.S. patent appears to be disadvantageous in that a complicated and time-consuming, precise connecting procedure is required to connect the manifold stampings together in a manner with the slots exactly aligned with the apertures. Even though the manifold stampings are exactly connected together, there will be a possibility that one manifold stamping once correctly connected with the other manifold stamping will rotate with the slots misaligned with the apertures during the final stage of the make-up of the catalytic converter.
The second mentioned U.S. patent discloses the use of the spacer in the form of a ring in combination with a perforated air supply tubing extending through a portion of the spacer ring and terminating in contact with the opposite portion of the spacer ring. This is complicated in structure and appears to require a relatively large number of component parts, thereby substantially reducing the workability of the converter and increasing the manufacturing cost.